I just bought a 93 Ls 400 a few days ago. The owner says he could never figure out how to keep the ac from shutting off after ~3 seconds of being on. He claimed the compressor was recently replaced and obviously freshly recharged, but it still would not stay on. I also notice a whine coming from the glove box area, which is where I believe the servos are located.

After running the AC diagnostic the only code that came back was 33 which is “Open in air mix damper position sensor circuit. Or, open or short in air mix servomotor circuit. Or, air mix servomotor locked."


I am not entirely sure what this means even after searching this and other forums. What I’ve concluded so far is it could either be; a bad relay, a ground connection that needs to be cleaned, a leak in the AC lines causing the compressor to lock up due to lack of refrigerant, a faulty servo, or a bad compressor (though I don’t think the previous owner was lying about replacing it).


I don’t really know where to begin. I’m not sure how to access the servos behind the glove box, or even diagnose what’s wrong with them. I’m not sure where the ground connections or relays I’m looking for are located either.


Any help would be greatly appreciated. I want an operational nut chiller, man.

 

I assume you went through this: http://www.lexls.com/tutorials/air/accodes.html

If you don't have a service manual that shows the suspected offending components, you may have to go through a Lexus parts diagram to locate the components. You'll still need some kind of diagnostic procedure to troubleshoot.